This invention relates to control valve arrangements for fluid systems and more particularly to providing improved productivity, uptime, and service replacement for such valves.
In many (if not all) fluid systems, one or more control valves are extremely critical to the functioning of the system. This is particularly true in connection with various types of machine tools or other manufacturing apparatuses wherein the control valves control certain operational functions. Because of the criticality and need for high performance, it is extremely desirable to insure that a system is provided wherein the entire operation will not be shut down if a defect occurs in one of the control valves. Therefore, one of the principal objects of this invention is to provide an improved control valve arrangement and replacement system for such apparatuses wherein failure of one control valve of the system will not render the entire system inoperative.
In connection with systems of this type it is extremely important that an arrangement be incorporated wherein a defective or malfunctioning control valve may be rapidly and conveniently replaced. That is, it is important to insure that a disabled control valve can be quickly removed for servicing and that the removal of this control valve does not shut the entire system down. Therefore, the present invention seeks to provide an improved and simplified arrangement for facilitating removal of a control valve for servicing or repair for a system without disabling the entire system.
The principles of the invention can be embodied in any of several forms that in most cases fall into one of four general categories. In one such category, an arrangement is provided wherein the failure or removal of a control valve results in maintaining the "status quo" of the overall system, i.e., maintaining an "air-on", pressurized condition. In this general category, as with the others discussed below, the apparatus for accomplishing this result can optionally be housed in a separate device or "block" interposed between the control valve and a system base. Such a system base has a plurality of flow ports sized and configured to match and align with the flow ports on the control valve, and but for the presence of the present invention, the control valve would normally have been mounted directly onto the system base. Thus, in order to allow for such a block to be interposed between the control valve and the base, the block must also have correspondingly sized and configured flow ports on both the control valve side and the base side of the block. Alternatively, the functional features of the interposed block can be housed or embodied directly in the system base, thus allowing for direct mounting of the control valve onto the base.
In a second general category, a pair of full-capacity control valves are provided, one of which being redundant or a backup with respect to the other, and thus only one control valve functions at a time. Each of such control valves is mounted onto a separate block somewhat similar to that described above and embodying the present invention. The blocks are mounted in turn onto the system base in an interposed relationship and function automatically to deactivate and isolate the functioning control valve in the event of its failure or removal and to activate the redundant or backup control valve, connecting it to the system for continued operation. Alternatively, the functional features of the separate interposed blocks can be housed or embodied directly in the system base, thus allowing for direct control valve mounting in a manner similar to that discussed above in connection with the first general category.
The third general category is functionally similar to the second general category discussed above (one of a number of full-capacity control valves functions at a time), except that the functional features of the separate interposed block are housed or embodied in a common block interposed between the two control valves and the system base. Alternatively, these functional features can be housed or embodied in the system base, and such an arrangement would thus be substantially the same, at least in function, as the above-discussed alternate arrangement for the second general category.
Finally, the fourth general category provides for a number of control valves functioning simultaneously under normal conditions. However, each of the control valves is over-sized with respect to such normal conditions, such that the failure or removal of one control valve leaves sufficient control valve capacity to allow for full, normal operation of the fluid system. In such an arrangement the present invention provides for maintenance of the "status quo" with respect to the failed or removed control valve in a manner generally similar to that described above in connection with the first general category.
An example of one arrangement falling within the fourth general category described above includes three or more half-capacity control valves, and thus allows for full system operation even if one of the control valves fails or is removed for service. According to the present invention, such "switching" between the operation of all valves and the operation of less than all valves occurs automatically in order to substantially eliminate, or at least minimize, system downtime. As with the other categories discussed above, the functional features of the invention can be housed or embodied in separate interposed blocks, in a common interposed block, or in the system base. The features of the invention described and illustrated herein, by way of merely exemplary embodiments, all fall generally into one or more of the four categories discussed above.
An advantage of most (if not all) embodiments of the present invention, and the preferred, proximal positioning of shutoff valves or other components of the invention with the control valves and the base, is to allow the control valves and the base to be under operative pressure so as to minimize pressure drop when one or the other of the control valves is activated during on-line operation of the system. This also allows for alternate employment of the control valves so as to eliminate the long term idleness of any one control valve. In addition, the alternate switching from one control valve to the other allows for important on-line functional testing of system components on a periodic basis.
One arrangement of the invention is adapted to be embodied in a control valve arrangement for a system having a powered device, such as an air cylinder or a hydraulic cylinder, for example, with a plurality of ports that are selectively communicated with a source of working fluid pressure or exhaust. A first control valve is movable between at least two positions, and a second control valve is likewise movable between at least two positions. Fluid circuitry communicates the first and second control valves in parallel with a source of working fluid pressure, with the ports of the powered device, and preferably also with an exhaust. First and second shutoff valves are provided in the fluid circuitry and are operable with the first and second control valves for selectively isolating the control valves from the working fluid pressure source, from the ports of the powered device, and in some cases from the exhaust, for replacement of one of the control valves with the other of the control valves controlling the powered device, thus effectively "switching" from a normal condition to a backup or redundant condition.
The embodiments of the invention are adapted to be used in combination with a base and a control valve having a mounting surface, wherein a shutoff valve assembly is interposed between the control valve and the base, or incorporated into the base. The shutoff valve assembly comprises a housing and internal workings with the housing having a surface on which the control valve mounting surface is removably mounted. Matching supply and outlet ports are formed in these surfaces and communicate with supply and outlet passages in the housing. Shutoff valve means are shiftably mounted in the housing for controlling the passages and are movable between an inactive or open position and a shutoff position. The shutoff valve assembly is responsive to fluid pressure changes caused by removal of the control valve mounting surface from the shutoff valve surface for causing the shutoff valve means to change from a normal condition to a shutoff condition. In addition, in at least some embodiments, the shutoff valve assembly can be manually activated to change from the normal condition to the shutoff condition.
Additional objects, advantages, and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.